Maleficent and magnificent are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Maleficent is an adjective. It means extremely evil or bad. Maleficent is one of several words that start with “mal” that relate to bad things.
Magnificent is an adjective. It means being impressive, being of high birth, possessing high level ability, or possessing high quality. It can also mean being a showstopper, putting on airs as if you are noble, amazing, etc.
The following story uses both words correctly:
Morgaine had a mixed reputation: those closest to her found her magnificent, but subordinates and strangers found her intimidating, selfish, even maleficent.